Self-heating sealant or adhesive employing multi-compartment microcapsules

ABSTRACT

A self-heating sealant or adhesive may be formed using multi-compartment microcapsules dispersed within a sealant or adhesive. The multi-compartment microcapsules produce heat when subjected to a stimulus (e.g., a compressive force, a magnetic field, or combinations thereof). In some embodiments, the multi-compartment microcapsules have first and second compartments separated by an isolating structure adapted to rupture in response to the stimulus, wherein the first and second compartments contain reactants that come in contact and react to produce heat when the isolating structure ruptures. In some embodiments, the multi-compartment microcapsules are shell-in-shell microcapsules each having an inner shell contained within an outer shell, wherein the inner shell defines the isolating structure and the outer shell does not allow the heat-generating chemistry to escape the microcapsule upon rupture of the inner shell.

BACKGROUND

The present invention relates in general to the field of materialsscience. More particularly, the present invention relates toself-heating sealants or adhesives employing multi-compartmentmicrocapsules for heat generation to enhance curing.

SUMMARY

A self-heating sealant or adhesive includes multi-compartmentmicrocapsules that increase the temperature of the sealant or adhesiveduring curing, e.g., during the process of assembling liquid crystalcells when a sealant is used to seal the periphery of a liquid crystallayer between a thin-film transistor (TFT) array substrate and a colorfilter substrate. Aspects of the present invention describe a method ofproducing a self-heating sealant or adhesive, a self-heating sealant oradhesive, and a method of curing a heat-sourcing sealant or adhesive.

According to some embodiments of the present invention, a self-heatingsealant or adhesive is prepared by dispersing multi-compartmentmicrocapsules within a sealant or adhesive. The multi-compartmentmicrocapsules produce heat when subjected to a stimulus (e.g., acompressive force, a magnetic field, ultrasound, or combinationsthereof). In some embodiments, the multi-compartment microcapsules havefirst and second compartments separated by an isolating structureadapted to rupture in response to the stimulus, wherein the first andsecond compartments contain reactants that come in contact and react toproduce heat when the isolating structure ruptures. In some embodiments,the multi-compartment microcapsules are shell-in-shell microcapsuleseach having an inner shell contained within an outer shell, wherein theinner shell defines the isolating structure and the outer shell does notallow the heat-generating chemistry to escape the microcapsule uponrupture of the inner shell.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Embodiments of the present invention will hereinafter be described inconjunction with the appended drawings, where like designations denotelike elements.

FIG. 1 illustrates a stage of TFT LCD panel fabrication (i.e., during aprocess of assembling liquid crystal cells) in which a self-heatingsealant is used to seal the periphery of a liquid crystal layer betweena TFT array substrate and a color filter substrate according to someembodiments of the present disclosure.

FIG. 2 illustrates a stage of TFT LCD panel fabrication (i.e., during aprocess of assembling LCD modules) in which a self-heating sealant isused as a terminal sealant according to some embodiments of the presentdisclosure.

FIG. 3A depicts a multi-compartment microcapsule having a shell-in-shellarchitecture with an inner shell contained within an outer shell,wherein the inner shell is adapted to rupture in response to acompressive force according to some embodiments of the presentdisclosure.

FIG. 3B depicts a multi-compartment microcapsule having an inner barrierto form compartments, wherein the inner barrier is adapted to rupture inresponse to a compressive force according to some embodiments of thepresent disclosure.

FIG. 3C depicts a multi-compartment microcapsule having a shell-in-shellarchitecture with an inner shell contained within an outer shell,wherein the inner shell is adapted to rupture in a magnetic fieldaccording to some embodiments of the present disclosure.

FIG. 4A illustrates a multi-compartment microcapsule containingreactants according to some embodiments of the present disclosure.

FIG. 4B illustrates a multi-compartment microcapsule in which thecapsule wall of the inner microcapsule is ruptured according to someembodiments of the present disclosure.

FIG. 4C illustrates a multi-compartment microcapsule in which a firstreactant is dispersed within a second reactant according to someembodiments of the present disclosure.

FIG. 4D illustrates a multi-compartment microcapsule in which thereactants within the microcapsule have generated heat according to someembodiments of the present disclosure.

FIG. 5 is an enlarged cutaway view of the liquid crystal cell shown inFIG. 1 in an earlier stage of TFT LCD panel fabrication (i.e., duringthe LCD module assembly process, but before the LCD panel end-sealsealant is applied), depicting LCD panel main sealant as a self-heatingsealant interspersed with multi-compartment microcapsules for heatgeneration according to some embodiments of the present disclosure.

FIG. 6 is a flow diagram illustrating, through stages 6(a)-6(f), amethod of producing a multi-compartment microcapsule having ashell-in-shell architecture with an inner shell contained within anouter shell, wherein the inner shell is adapted to rupture in responseto a compressive force and/or a magnetic field according to someembodiments of the present disclosure.

FIG. 7 is a flow diagram illustrating an exemplary method of producing aself-heating sealant or adhesive according to some embodiments of thepresent disclosure.

FIG. 8 is a flow diagram illustrating an exemplary method of curing aself-heating sealant or adhesive according to some embodiments of thepresent disclosure.

FIG. 9 is a flow diagram illustrating, through stages 9(a)-9(e), amethod of assembling liquid crystal cells during TFT LCD panelfabrication, in which a self-heating sealant is used to seal theperiphery of a liquid crystal layer between a TFT array substrate and acolor filter substrate according to some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to a self-heating sealant oradhesive having multi-compartment microcapsules dispersed within asealant or adhesive. Other aspects of the present disclosure relate to amethod of producing a self-heating sealant or adhesive havingmulti-compartment microcapsules dispersed within a sealant or adhesive.Still other aspects of the present disclosure relate to a method ofcuring a self-heating sealant or adhesive having multi-compartmentmicrocapsules dispersed within the sealant or adhesive. Yet otheraspects of the present disclosure relate to forming and activatingmulti-compartment microcapsules for heat generation in sealants,adhesives, or other materials that would benefit from their inclusionsuch as thermal interface materials (TIMs), coatings, paints, varnishes,encapsulants, and the like.

Benefits that may be achieved by inclusion of multi-compartmentmicrocapsules for heat generation in materials such as sealants,adhesives, TIMs, coatings, paints, varnishes, encapsulants, and thelike, include, but are not limited to, reduced cure time, reducedviscosity, and increased compliance. Compliance is a measure of theability of a material to flow. Materials with a lower compliance producethicker bond lines. Heating a material through activation ofmulti-component microcapsules including the material for heat generationmay increase its compliance and correspondingly produce a thinner bondline.

A self-heating sealant or adhesive, in accordance with some embodimentsof the present disclosure, comprises multi-compartment microcapsulesdispersed within a sealant or adhesive. The multi-compartmentmicrocapsules produce heat when subjected to a stimulus (e.g., acompressive force, a magnetic field, ultrasound, or combinationsthereof). In some embodiments, the multi-compartment microcapsules havefirst and second compartments separated by an isolating structureadapted to rupture in response to the stimulus, wherein the first andsecond compartments contain reactants that come in contact and react toproduce heat when the isolating structure ruptures. In some embodiments,the multi-compartment microcapsules are shell-in-shell microcapsuleseach having an inner shell contained within an outer shell, wherein theinner shell defines the isolating structure and the outer shell does notallow the heat-generating chemistry to escape the microcapsule uponrupture of the inner shell.

Sealants and adhesives are often pigeon-holed together, but these termsare not always interchangeable. An adhesive is designed to bond two ormore items together. A sealant is designed to fill a gap between two ormore items to prevent contaminants (e.g., moisture and gases) frominfiltrating therebetween. An adhesive is not necessarily a sealant, andvisa-versa.

Multi-compartment microcapsules are known in the art to be formed in avariety of structural configurations (e.g., concentric, pericentric,innercentric, or acentric). Multi-compartment microcapsules include atleast two compartments that are separated from each other. Thecompartments within a multi-compartment microcapsule may contain variouschemical elements or compounds. Multi-compartment microcapsules may beproduced using techniques well known to those skilled in the art.

In the embodiments that follow, exemplary self-heating sealants andexemplary self-heating adhesives are employed in the context ofthin-film transistor (TFT) liquid crystal display (LCD) panelfabrication. These exemplary self-heating sealants and adhesives are setforth for purposes of illustration, not limitation. One skilled in theart will appreciate that a self-heating sealant or adhesive consistentwith the spirit of the present disclosure may be used in other contexts.

Sealants and adhesives are used in many stages of TFT LCD panelfabrication, including the liquid crystal cell assembly process and theLCD module assembly process.

For example, during the process of assembling liquid crystal cells(i.e., also referred to as the liquid crystal cell assembly process), asealant is used to seal the periphery of a liquid crystal layer betweena TFT array substrate and a color filter substrate. The substrates arebrought together with the sealant interposed therebetween at theperiphery of the substrates while a cell gap between the substrates ismaintained by spacers. Two main types of conventional sealants are usedduring this stage of LCD manufacturing: thermally-cured sealants (e.g.,epoxy resin) and UV-cured sealants (e.g., acrylic resin). Theseconventional sealants are typically applied by screen-printing orthrough the use of sealant dispensers (e.g., one or more dispensingheads). Unfortunately, these conventional sealants typically impedespeeding up production and achieving higher unit-volume throughputbecause they require the use of heat ovens and/or ultraviolet lamps.

FIG. 1 illustrates a stage of TFT LCD panel fabrication (i.e., during aprocess of assembling a liquid crystal cell 100) in which a self-heatingsealant (e.g., an LCD panel main sealant 102 and/or an LCD panel endsealant 104) is used to seal the periphery of a liquid crystal layer(not shown in FIG. 1) between a TFT array substrate 106 and a colorfilter substrate 108 according to some embodiments of the presentdisclosure. In accordance with some embodiments of the presentdisclosure, the LCD panel main sealant 102 may be a self-heating sealanthaving multi-compartment microcapsules dispersed in a resin (epoxy)based sealant, such as UV- and heat-curable epoxy resins. Themulti-compartment microcapsules contained in the LCD panel main sealant102 may be activated, for example, by a compressive force applied viapressure bonding when the substrates 106, 108 are brought together withthe LCD panel main sealant 102 interposed therebetween. Similarly, inaccordance with some embodiments of the present disclosure, the LCDpanel end sealant 104 may be a self-heating sealant havingmulti-compartment microcapsules dispersed in a resin (epoxy) basedsealant, such as UV- and heat-curable epoxy resins. Themulti-compartment microcapsules contained in the LCD panel end sealant104 may be activated, for example, by a compressive force applied by asealant dispenser (e.g., a dispensing head used to dispense the LCDpanel end sealant 104). An exemplary process of assembling a liquidcrystal cell during TFT LCD panel fabrication, in which a self-heatingsealant is used in accordance with some embodiments of the presentdisclosure, is described below with reference to FIG. 9.

FIG. 2 illustrates a stage of TFT LCD panel fabrication (i.e., during aprocess of assembling LCD module 200) in which a self-heating sealant(e.g., a terminal sealant 202) is used to seal the transparentdisplay/backlight electrodes of the LCD module 200 and a self-heatingadhesive (e.g., an anisotropically conductive adhesive 204) is used toform mechanical bonding and electrical connections between thetransparent display/backlight electrodes of the LCD module 200 and adriver flexible printed circuit (FPC) 214 according to some embodimentsof the present disclosure.

A transparent, electrically conductive indium tin oxide (ITO) layer 206,which provides transparent display/backlight panel electrodes of the LCDmodule 200, is sputter deposited on a glass substrate 208 of the TFTarray substrate 106. Similarly, an ITO layer 210 is sputter deposited onthe glass substrate 212 of the color filter substrate 108. Theanisotropically conductive adhesive 204, which is used to formmechanical bonding and electrical connections between the transparentdisplay/backlight electrodes and a driver FPC 214, cures to provide ananisotropically conductive film (ACF) 216. In accordance with someembodiments of the present disclosure, the anisotropically conductiveadhesive 204 may be a self-heating adhesive having multi-compartmentmicrocapsules dispersed in an anisotropically conductive adhesive, suchas ThreeBond 3370G. Anisotropically conductive adhesives (which are alsoreferred to as “anisotropically conductive pastes”) are typically madeof thermoplastic resin in which a conductive filler is dispersed. Themulti-compartment microcapsules contained in the anisotropicallyconductive adhesive 204 may be activated, for example, by a compressiveforce applied via pressure bonding when the ITO layer 206/glasssubstrate 208 and the driver FPC 214 are brought together with theanisotropically conductive adhesive 204 interposed therebetween.

The terminal sealant 202, which seals the display/backlight electrodesof the LCD module 200, preferably has strong adhesion to the glasssubstrates 208, 212, the ITO layers 210, 206, the driver FPC 214, andthe ACF 216. In accordance with some embodiments of the presentdisclosure, the terminal sealant 202 may be a self-heating sealanthaving multi-compartment microcapsules dispersed in a silicone sealant,such as Dow Corning SE9187 L or Dow Corning EA-3000. Themulti-compartment microcapsules contained in the terminal sealant 202may be activated, for example, by a compressive force applied by asealant dispenser (e.g., a dispensing head used to dispense the terminalsealant 202).

FIG. 3A depicts a multi-compartment microcapsule 300 having ashell-in-shell architecture with an inner shell contained within anouter shell, wherein the inner shell is adapted to rupture in responseto a compressive force according to some embodiments of the presentdisclosure. In FIG. 3A, the multi-compartment microcapsule 300 isillustrated in a cutaway view. The multi-compartment microcapsule 300has an outer wall 301 (also referred to herein as the “outer shell” 301of the multi-compartment microcapsule 300) and contains an innermicrocapsule 302 and a first reactant 303. The inner microcapsule 302has a capsule wall 304 (also referred to herein as the “inner shell” 304of the multi-compartment microcapsule 300) and contains a secondreactant 305. The first reactant 303 within the multi-compartmentmicrocapsule 300 may surround the inner microcapsule 302, and the firstreactant 303 may be prevented from contacting the second reactant 305 bythe capsule wall 304 of the inner microcapsule 302.

The capsule wall 304 of the inner microcapsule 302 may be formed torupture under a particular compressive force and the outer wall 301 ofthe microcapsule 300 may be formed so as to not rupture under thatcompressive force. Rupturing the capsule wall 304 of the innermicrocapsule 302 may allow the second reactant 305 to contact the firstreactant 303 and the reactants may then chemically or physically react.In various embodiments, the reaction may be exothermic.

FIG. 3B depicts a multi-compartment microcapsule 310 having an innerbarrier to form compartments, wherein the inner barrier is adapted torupture in response to a compressive force according to some embodimentsof the present disclosure. In FIG. 3A, the multi-compartmentmicrocapsule 310 is illustrated in a cutaway view. The multi-compartmentmicrocapsule 310 has an outer wall 311 and contains a first reactant 313and a second reactant 315. A membrane 314 within the multi-compartmentmicrocapsule 310 may prevent the first reactant 313 and the secondreactant 315 from coming into contact. The membrane 314 may be any formof a physical barrier that forms two or more compartments within themicrocapsule 310.

The membrane 314 may be formed to rupture under a particular compressiveforce and the outer wall 311 of the multi-compartment microcapsule 310may be formed so as to not rupture under that compressive force.Rupturing the membrane 314 may allow the first reactant 313 to contactthe second reactant 315 and the reactants may then chemically orphysically react. In various embodiments, the reaction may beexothermic.

In accordance with some embodiments, the compressive force applied to aself-heating sealant or adhesive may be within the range typical of thatapplied in the manufacture or repair of electronic assemblies (e.g.,during the process of assembling liquid crystal cells, during theprocess of assembling LCD modules, and the like). In accordance withsome embodiments, the inner capsule wall 304 (of the multi-compartmentmicrocapsule 300 shown in FIG. 3A), or a membrane 314 (of themulti-compartment microcapsule 310 shown in FIG. 3B), may rupture at aforce no greater than the lower bound of this range of compressiveforce. The outer wall 301 (of the multi-compartment microcapsule 300shown in FIG. 3A), or the outer wall 311 (of the multi-compartmentmicrocapsule 310 shown in FIG. 3B), may sustain, without rupturing, aforce no less than the upper bound of this range of compressive force.

Other embodiments may utilize more than two reactants. Themulti-compartment microcapsule 300 of FIG. 3A may contain a plurality ofinner microcapsules, such as 302, and the inner microcapsules maythemselves contain other, inner, microcapsules. The variousmicrocapsules may contain reactants and may rupture under compression toallow the reactants to come into contact. Similarly, themulti-compartment microcapsule 310 of FIG. 3B may contain a plurality ofcompartments formed by a plurality of membranes or barriers, such as314, and the compartments may in turn contain one or more membranes orbarriers, or may contain microcapsules. The various membranes orbarriers may rupture under compression to allow the reactants to comeinto contact.

FIG. 3C depicts a multi-compartment microcapsule 320 having ashell-in-shell architecture with an inner shell contained within anouter shell, wherein the inner shell is adapted to rupture in a magneticfield according to some embodiments of the present disclosure. In FIG.3C, the multi-compartment microcapsule 320 is illustrated in a cutawayview. The multi-compartment microcapsule 320 depicted in FIG. 3C issimilar to the multi-compartment microcapsule 300 depicted in FIG. 3A,but one or more magnetic nanoparticles 330 are incorporated into theinner shell of the multi-compartment microcapsule 320. Themulti-compartment microcapsule 320 has an outer wall 321 (also referredto herein as the “outer shell” 321 of the multi-compartment microcapsule320) and contains an inner microcapsule 322 and a first reactant 323.The inner microcapsule 322 has a capsule wall 324 (also referred toherein as the “inner shell” 324 of the multi-compartment microcapsule320) and contains a second reactant 325. The first reactant 323 withinthe multi-compartment microcapsule 320 may surround the innermicrocapsule 322, and the first reactant 323 may be prevented fromcontacting the second reactant 325 by the capsule wall 324 of the innermicrocapsule 322.

With regard to the multi-compartment microcapsule 320 depicted in FIG.3C, in accordance with some embodiments of the present disclosure, amagnetic field generating device generates a magnetic field sufficientto rupture the “inner shell” 324 of the multi-compartment microcapsules320 dispersed in a sealant or adhesive through magnetic stimulation ofthe magnetic nanoparticles 330. Application of a sufficiently stronghigh-frequency magnetic field causes the magnetic nanoparticles 330embedded in the “inner shell” 324 of the multi-compartment microcapsules320 to rotate and/or vibrate at an accelerated rate thereby rupturingthe “inner shell” 324 and, in turn, permit the first reactant 323 andthe second reactant 325 to contact one another, react, and generateheat. Preferably, the high-frequency magnetic field applied to theself-heating sealant or adhesive by the magnetic field generating devicehas a frequency of approximately 50-100 kHz and a strength ofapproximately 2.5 kA/m or 31 Oe.

The capsule wall 324 of the inner microcapsule 322 may be formed withone or more magnetic nanoparticles 330 to rupture under a particularmagnetic field through magnetic stimulation of the one or more magneticnanoparticles 330 and the outer wall 321 of the microcapsule 320 may beformed so as to not rupture under that magnetic field. Rupturing thecapsule wall 324 of the inner microcapsule 322 may allow the secondreactant 325 to contact the first reactant 323 and the reactants maythen chemically or physically react. In various embodiments, thereaction may be exothermic.

FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D illustrate configurations of amicrocapsule under a compressive force, and the compression causing thereactants within the microcapsule to mix, according to some embodimentsof the present disclosure. FIG. 4A illustrates a first microcapsulecontaining reactants and an inner microcapsule. FIG. 4B illustrates thefirst microcapsule of FIG. 4A in which the inner microcapsule wall isruptured. FIG. 4C illustrates the first microcapsule of FIG. 4B in whicha reactant contained in the inner microcapsule is dispersed within areactant initially surrounding the inner microcapsule. FIG. 4Dillustrates the first microcapsule of FIG. 4C in which the reactantshave produced a reaction product within the first microcapsule andgenerated heat.

In more detail, FIG. 4A illustrates a microcapsule 400 formed to have astructure similar to that of the multi-compartment microcapsule 300 ofFIG. 3A. Microcapsule 400 may have an outer wall 401 and may contain afirst reactant 403 and an inner capsule 402 a. The inner capsule 402 amay have an outer capsule wall 404 a and may contain a second reactant405 a.

A compressive force may be applied to the multi-compartment microcapsule400, which may cause the capsule wall 404 a of an inner microcapsule 402a to rupture. FIG. 4B illustrates a second configuration of microcapsule400 in which the capsule wall 404 b of the inner microcapsule 402 b mayrupture under compression of the microcapsule 400, indicated by thebroken line of the capsule wall 404 b. FIG. 4C illustrates a thirdconfiguration of microcapsule 400 in which the second reactant 405 c maybecome dispersed within the first reactant 403 c, in response to theinner microcapsule 402 b having ruptured. The dispersion of the secondreactant 405 c within the first reactant 403 c may cause them to react.

FIG. 4D illustrates a fourth configuration of microcapsule 400 in whichthe reactants 403 c and 405 c may have come into contact and may havereacted. The fourth configuration of the microcapsule 400 may containthe product 405 d of the reaction of 403 c and 405 c and the outer wall401 may contain the reaction product 405 d so as to prevent the reactionproduct from contacting a material in which microcapsule 400 may beitself dispersed. The reactants 403 c and 405 c may have reactedexothermically to produce heat 416, and the heat may, as illustrated inFIG. 4D, transfer from the microcapsule 400 to a material in which themicrocapsule is dispersed.

In accordance with some embodiments of the present disclosure, aself-heating sealant or adhesive may utilize a multi-compartmentmicrocapsule containing an oxidizing and a reducing agent to produce anexothermic reaction, such as oxygen and iron, respectively, according tothe reaction equation:

4Fe(s)+3O₂(g)===>2Fe₂O₃(s)Hrxn=−1.65103 kJ

According to the reaction equation, 4 moles of iron react with 3 molesof oxygen, such that in an embodiment iron may comprise 53% of thecombined mass of the two reactants and oxygen may comprise 43% of thatcombined mass. In an additional embodiment, a multi-compartmentmicrocapsule may contain iron powder and hydrogen peroxide. The ironpowder may be mixed with a catalyst such as ferric nitrate, which whenin contact with the hydrogen peroxide liberates oxygen to reactexothermically with the iron powder. For example, the multi-compartmentmicrocapsule may use 1.5 moles of hydrogen peroxide per mole of iron,for example 0.56 grams of iron powder to 0.51 grams of hydrogenperoxide. The catalytic amount of ferric nitrate may be chosen toachieve a desired reaction rate of heating, in Kilojoules per second.For example, between 0.001 and 0.005 gram equivalents of ferric nitrateper liter of hydrogen peroxide results in a reaction rate producing heatat between 100 and 500 Kilojoules per second.

With reference again to the multi-compartment microcapsule 300 of FIG.3A, a multi-compartment microcapsule may contain a mixture of ironpowder and ferric nitrate in the inner microcapsule 302 as the secondreactant 305 and may contain hydrogen peroxide as the first reactant 303surrounding the inner microcapsule 302. Alternatively, amulti-compartment microcapsule may contain hydrogen peroxide in theinner microcapsule 302 as the second reactant 305 and may contain amixture of iron powder and ferric nitrate as the first reactant 303surrounding the inner microcapsule 302. In some embodiments, amulti-compartment microcapsule may have a diameter of less than 5.0microns, or a multi-compartment microcapsule may have a smaller diameterof less than 2.0 microns. A ratio of 0.2 percent of suchmulti-compartment microcapsules per unit mass of the sealant or adhesivemay produce a temperature increase of at least 1.04 degrees C. per gramof sealant or adhesive.

A structure similar to multi-compartment microcapsule 310 of FIG. 3B,including the various embodiments thereof, may operate similarly to themicrocapsule 400 of FIG. 4A through FIG. 4D to rupture the membrane 314,mix the reactants 313 and 315, and produce heat from an exothermicreaction 416 of the reactants. It would be further apparent to one ofordinary skill in that art that an exothermic reaction may be producedby more than two reactants, and that more than two reactants within acapsule may be isolated by more than one inner capsule or membrane, ormore than one of any other form of barrier isolating the reactantswithin the capsule. A variety of reactants may be substituted to producean exothermic reaction, or a variety of reaction rates and total heatproduced, in accordance with some embodiments of the present disclosure.

FIG. 5 is an enlarged cutaway view of the liquid crystal cell 100 shownin FIG. 1 in an earlier stage of TFT LCD panel fabrication (i.e., duringthe LCD module assembly process, but before the LCD panel end-sealsealant 104 shown in FIG. 1 is applied), depicting the LCD panel mainsealant 102 as a self-heating sealant interspersed withmulti-compartment microcapsules 501 for heat generation according tosome embodiments of the present disclosure. The LCD panel main sealant102 contacts the TFT array substrate 106 at surface 506 and the colorfilter substrate 108 at surface 508, and may have a bond line (i.e., themass of the sealant 102 between surfaces 506 and 508) thickness T1 atambient temperatures. The LCD panel main sealant 102 may have dispersedwithin it a plurality of multi-compartment microcapsules 501 forgenerating heat in response to a stimulus, such as a compressive force,a magnetic field, and the like.

For example, in accordance with some embodiments of the presentdisclosure, when the LCD panel main sealant 102 is compressed betweenthe TFT array substrate 106 and the color filter substrate 108, themulti-compartment microcapsules 501 may initiate a reaction and thereaction may produce heat. Alternatively, in accordance with otherembodiments of the present disclosure, when the LCD panel main sealant102 interposed between the TFT array substrate 106 and the color filtersubstrate 108 and subjected to a magnetic field, the multi-compartmentmicrocapsules 501 may initiate a reaction and the reaction may produceheat. The heat may be transferred to the LCD panel main sealant 102, andheating the LCD panel main sealant 102 may cure the LCD panel mainsealant 102. In addition, heating the LCD panel main sealant 102 mayincrease the compliance of the LCD panel main sealant 102. Increasingthe compliance of the LCD panel main sealant 102 may produce a bond linethickness of the LCD panel main sealant 102 less than Ti. In the variousembodiments, the multi-compartment microcapsules 501 may be a structuresimilar to the multi-compartment microcapsule 300 or 310 as described inreference to FIG. 3A and FIG. 3B, respectively, or may be a structuresimilar to the multi-compartment microcapsule 320 as described inreference to FIG. 3C. Some embodiments of the present disclosure maydisperse multi-compartment microcapsules 501, such as microcapsules 300,310, or 320, in an LCD panel main sealant 102, and an LCD panel mainsealant 102 may be an epoxy-based sealant, an acrylic-based sealant, asilicone-based sealant, and combinations thereof.

FIG. 6 is a flow diagram illustrating, through stages 6(a)-6(f), amethod 600 of producing a multi-compartment microcapsule having ashell-in-shell architecture with an inner shell contained within anouter shell, wherein the inner shell is adapted to rupture in responseto a compressive force and/or a magnetic field according to someembodiments of the present disclosure. In the method 600, the stepsdiscussed below (steps 605-625) are performed. These steps are set forthe in their preferred order. It must be understood, however, that thevarious steps may occur simultaneously or at other times relative to oneanother. Moreover, those skilled in the art will appreciate that one ormore steps may be omitted.

In method 600, magnetic nanoparticles are used in step 605 forincorporation into the “inner core” CaCO₃ microparticles (shown at stage6(b)) and, optionally, in step 610 for incorporation into the “innershell” polyelectrolyte multilayer (i.e., the “Polymer” shown at stage6(c)). Magnetic nanoparticles are incorporated into the “inner core”CaCO₃ microparticles for the purpose of subsequently magneticallyisolating the product prepared in step 615 (i.e., ball-in-ball CaCO₃microparticles) from a coproduct (i.e., single core CaCO₃microparticles). Magnetic nanoparticles are optionally incorporated intothe “inner shell” polyelectrolyte multilayer for the purpose of adaptingthe inner shell of the shell-in-shell microcapsule to rupture inresponse to a magnetic field. The shell-in-shell microcapsule thatresults from this optional incorporation of magnetic nanoparticles intothe inner shell corresponds to the multi-compartment microcapsule shownin FIG. 3C.

The magnetic nanoparticles may be, for example, Fe₃O₄ (also referred toas “magnetite”) nanoparticles, cobalt ferrite nanoparticles, or othermagnetic nanoparticles known in the art. Preferably, the magneticnanoparticles have a diameter in the range of approximately 6-25 nm.

The magnetic nanoparticles are prepared using conventional techniquesknown to those skilled in the art. For example, magnetite nanoparticlesmay be prepared using a conventional technique known as the“coprecipitation method.” See, for example, the discussion of preparingmagnetite nanoparticles using the coprecipitation method in the articleto M. Yamaura et al., “Preparation and characterization of(3-aminopropyl) triethoxysilane-coated magnetite nanoparticles,” Journalof Magnetism and Magnetic Materials, Vol. 279, pages 210-217, 2004,which is hereby incorporated herein by reference in its entirety.

An example of a conventional technique of preparing magnetitenanoparticles follows. This conventional example is based on an exampleset forth in the M. Yamaura et al. article. A 5 mol/l NaOH solution isadded into a mixed solution of 0.25 mol/l ferrous chloride and 0.5 mol/lferric chloride (molar ratio 1:2) until obtaining pH 11 at roomtemperature. The slurry is washed repeatedly with distilled water. Then,the resulting magnetite nanoparticles are magnetically separated fromthe supernatant and redispersed in aqueous solution at least threetimes, until obtaining pH 7. The M. Yamaura et al. article reports thata typical average diameter of the resulting magnetite nanoparticles is12 nm.

In each of the stages 6(a)-6(f), the structure is shown in across-sectional side view. The method 600 is a modified version of theshell-in-shell microcapsule concept disclosed in Kreft et al.,“Shell-in-Shell Microcapsules: A Novel Tool for Integrated, SpatiallyConfined Enzymatic Reactions”, Angewandte Chemie International Edition,Vol. 46, 2007, pp. 5605-5608, which is hereby incorporated herein byreference in its entirety.

The method 600 begins by preparing spherical calcium carbonatemicroparticles in which finely powdered iron and magnetite nanoparticlesare immobilized by coprecipitation (step 605). Optionally, a catalystsuch as ferric nitrate may be immobilized in the spherical calciumcarbonate microcapsules as well as the iron powder and the magnetitenanoparticles. For example, 1M CaCl₂ (0.615 mL), 1M Na₂CO₃ (0.615 mL),1.4% (w/v) magnetite nanoparticle suspension (50 μL) and deionized water(2.450 mL) containing finely powdered iron (2 mg) and, optionally,Fe(NO₃)₃ (0.01 mg) may be rapidly mixed and thoroughly agitated on amagnetic stirrer for 20 s at room temperature. After the agitation, theprecipitate may be separated from the supernatant by centrifugation andwashed three times with water. One of the resulting CaCO₃ microparticlesis shown at stage 6(b).

The diameter of the CaCO₃ microparticles produced with a reaction timeof 20 s is 4-6 μm. Smaller CaCO₃ microparticles are produced if thereaction time is reduced from 20 s to several seconds.

One skilled in the art will appreciate that other metals may be used inlieu of, or in addition to, the iron powder. For example, magnesium ormagnesium-iron alloy may also be used.

One skilled in the art will appreciate that other magnetic nanoparticlesmay be used in lieu of, or in addition to, the magnetite. For example,cobalt ferrite nanoparticles may also be used.

As noted above, the iron powder may be mixed with a catalyst such asferric nitrate, which when in contact with the hydrogen peroxide (to beencapsulated in the outer shell) liberates oxygen to reactexothermically with the iron powder. One skilled in the art willappreciate that other catalysts may be used in lieu of, or in additionto, the ferric nitrate. For example, sodium iodide (NaI) may also beused.

In this example, the fabrication of polyelectrolyte capsules is based onthe layer-by-layer (LbL) self-assembly of polyelectrolyte thin films.Such polyelectrolyte capsules are fabricated by the consecutiveadsorption of alternating layer of positively and negatively chargedpolyelectrolytes onto sacrificial colloidal templates. Calcium carbonateis but one example of a sacrificial colloidal template. One skilled inthe art will appreciate that other templates may be used in lieu of, orin addition to, calcium carbonate. For example, in accordance with otherembodiments of the present disclosure, polyelectrolyte capsules may betemplated on melamine formaldehyde and silica.

The method 600 continues by LbL coating the CaCO₃ microparticles (step610). In step 610, a polyelectrolyte multilayer (PEM) build-up may beemployed by adsorbing five bilayers of negative PSS (poly(sodium4-styrenesulfonate); Mw=70 kDa) and positive PAH (poly(allylaminehydrochloride); Mw=70 kDa) (2 mg/mL in 0.5 M NaCl) by using thelayer-by-layer assembly protocol. For example, the CaCO₃ microparticlesproduced in step 605 may be dispersed in a 0.5 M NaCl solution with 2mg/mL PSS (i.e., polyanion) and shaken continuously for 10 min. Theexcess polyanion may be removed by centrifugation and washing withdeionized water. Then, 1 mL of 0.5 M NaCl solution containing 2 mg/mLPAH (i.e., polycation) may be added and shaken continuously for 10 min.The excess polycation may be removed by centrifugation and washing withdeionized water. This deposition process of oppositely chargedpolyelectrolyte may be repeated five times and, consequently, fivePSS/PAH bilayers are deposited on the surface of the CaCO₃microparticles. One of the resulting polymer coated CaCO₃ microparticlesis shown at stage 6(c).

Alternatively, as noted above, in step 610, magnetic nanoparticles maybe used in the polyelectrolyte multilayer (PEM) build-up. That is,magnetic nanoparticles may be incorporated into the “inner shell”polyelectrolyte multilayer for the purpose of adapting the inner shellof the shell-in-shell microcapsule to rupture in responsive to amagnetic field. The shell-in-shell microcapsule that results from thisoptional incorporation of magnetic nanoparticles into the inner shellcorresponds to the multi-compartment microcapsule shown in FIG. 3C. Forexample, the CaCO₃ microparticles produced in step 605 may be dispersedin a 0.5 M NaCl solution with Fe₃O₄ nanoparticles (citric acid modified,2 mg/mL) and shaken continuously for 10 min. The excess magnetitenanoparticles may be removed by centrifugation and washing withdeionized water. Then, 1 mL of 0.5 M NaCl solution containing 2 mg/mLPAH (polycation) may be added and shaken continuously for 10 min. Theexcess polycation may be removed by centrifugation and washing withdeionized water. This deposition process may be repeated five times and,consequently, five Fe₃O₄/PAH bilayers are deposited on the surface ofthe CaCO₃ microparticles.

One skilled in the art will appreciate that other magnetic nanoparticlesmay be used in lieu of, or in addition to, the Fe₃O₄ nanoparticles. Forexample, cobalt ferrite nanoparticles may also be used.

The thickness of this “inner shell” polyelectrolyte multilayer may bevaried by changing the number of bilayers. Generally, it is desirablefor the inner shell to rupture while the outer shell remains intact sothat the reactants and the reaction products do not contaminate thesealant or adhesive into which the multi-compartment microcapsule may bedispersed. Typically, for a given shell diameter, thinner shells rupturemore readily than thicker shells. Hence, in accordance with someembodiments of the present disclosure, the inner shell is maderelatively thin compared to the outer shell. On the other hand, theinner shell must not be so thin as to rupture prematurely.

The PSS/PAH-multilayer in step 610, is but one example of apolyelectrolyte multilayer. One skilled in the art will appreciate thatother polyelectrolyte multilayers and other coatings may be used in lieuof, or in addition to, the PSS/PAH-multilayer in step 610. For example,coating polyelectrolyte multilayer capsules with lipids can result in asignificant reduction of the capsule wall permeability.

The method 600 continues by preparing ball-in-ball calcium carbonatemicroparticles in which hydrogen peroxide is immobilized by a secondcoprecipitation (step 615). The ball-in-ball CaCO₃ microparticles arecharacterized by a polyelectrolyte multilayer that is sandwiched betweentwo calcium carbonate compartments. In step 615, the polymer coatedCaCO₃ microparticles may be resuspended in 1M CaCl₂ (0.615 mL), 1MNa₂CO₃ (0.615 mL), and deionized water (2.500 mL) containing hydrogenperoxide (1 mg), rapidly mixed and thoroughly agitated on a magneticstirrer for 20 s at room temperature. After the agitation, theprecipitate may be separated from the supernatant by centrifugation andwashed three times with water. Unfortunately, the second coprecipitationis accompanied by formation of a coproduct, i.e., single core CaCO₃microparticles that contain only hydrogen peroxide. Hence, the resultingprecipitate represents a mixture of ball-in-ball CaCO₃ microparticlesand single core CaCO₃ microparticles. The ball-in-ball CaCO₃microparticles, which are magnetic due to the immobilized magnetitenanoparticles in the inner compartment, may be isolated by applying anexternal magnetic field to the sample while all of the nonmagneticsingle core CaCO₃ microparticles are removed by a few washing steps. Oneof the resulting ball-in-ball CaCO₃ microparticles is shown at stage6(d).

One skilled in the art will appreciate that other oxidizers may be usedin lieu of, or in addition to, the hydrogen peroxide. For example, watermay also be used.

The method 600 continues by LbL coating the ball-in-ball CaCO₃microparticles (step 620). In step 620, a polyelectrolyte multilayer(PEM) build-up may be employed by adsorbing five bilayers of negativePSS (poly(sodium 4-styrenesulfonate); Mw=70 kDa) and positive PAH(poly(allylamine hydrochloride); Mw=70 kDa) (2 mg/mL in 0.5 M NaCl) byusing the layer-by-layer assembly protocol. For example, theball-in-ball CaCO₃ microparticles produced in step 615 may be dispersedin a 0.5 M NaCl solution with 2 mg/mL PSS (i.e., polyanion) and shakencontinuously for 10 min. The excess polyanion may be removed bycentrifugation and washing with deionized water. Then, 1 mL of 0.5 MNaCl solution containing 2 mg/mL PAH (i.e., polycation) may be added andshaken continuously for 10 min. The excess polycation may be removed bycentrifugation and washing with deionized water. This deposition processof oppositely charged polyelectrolyte may be repeated five times and,consequently, five PSS/PAH bilayers are deposited on the surface of theball-in-ball CaCO₃ microparticles. One of the resulting polymer coatedball-in-ball CaCO₃ microparticles is shown at stage 6(e).

The thickness of this “outer shell” polyelectrolyte multilayer may bevaried by changing the number of bilayers. Generally, it is desirablefor the inner shell to rupture while the outer shell remains intact sothat the reactants and the reaction products do not contaminate thesealant or adhesive into which the multi-compartment microcapsule isdispersed. Typically, for a given shell diameter, thinner shells rupturemore readily than thicker shells. Hence, in accordance with someembodiments of the present disclosure, the outer shell is maderelatively thick compared to the inner shell.

The PSS/PAH-multilayer in step 620, is but one example of apolyelectrolyte multilayer. One skilled in the art will appreciate thatother polyelectrolyte multilayers and other coatings may be used in lieuof, or in addition to, the PSS/PAH-multilayer in step 620. As notedabove, coating polyelectrolyte multilayer capsules with lipids, forexample, can result in a significant reduction of the capsule wallpermeability.

The method 600 concludes with CaCO₃ extraction (step 625). In step 625,the CaCO₃ core of the ball-in-ball CaCO₃ microparticles may be removedby complexation with ethylenediaminetetraacetic acid (EDTA) (0.2 M, pH7.5) leading to formation of shell-in-shell microcapsules. For example,the ball-in-ball CaCO₃ microparticles produced in step 620 may bedispersed in 10 mL of the EDTA solution (0.2 M, pH 7.5) and shaken for 4h, followed by centrifugation and re-dispersion in fresh EDTA solution.This core-removing process may be repeated several times to completelyremove the CaCO₃ core. The size of the resulting shell-in-shellmicrocapsules ranges from 8-10 μm and the inner core diameter is 3-5 μm.One of the resulting shell-in-shell microcapsules is shown at stage6(f).

As noted above, the fabrication of polyelectrolyte capsules in method600 is based on the layer-by-layer (LbL) self-assembly ofpolyelectrolyte thin films. One skilled in the art will appreciate thata multi-compartment microcapsule for heat generation in accordance withsome embodiments of the present disclosure may be produced by otherconventional multi-compartment systems, such as polymeric micelles,hybrid polymer microspheres, and two-compartment vesicles.

FIG. 7 is a flow diagram illustrating an exemplary method 700 ofproducing a self-heating sealant or adhesive according to someembodiments of the present disclosure. In the method 700, the stepsdiscussed below (steps 710-740) are performed. These steps are set forthe in their preferred order. It must be understood, however, that thevarious steps may occur simultaneously or at other times relative to oneanother. Moreover, those skilled in the art will appreciate that one ormore steps may be omitted.

FIG. 7 exemplifies a method 700 of producing a self-heating sealant oradhesive, particularly in an embodiment using a multi-compartmentmicrocapsule having a shell-in-shell architecture. Various manners ofmodifying or adapting the method to a variety of embodiments, includingother embodiments of a multi-compartment microcapsule to disperse withina sealant or adhesive, will be apparent to one of ordinary skill in theart. The method 700 should be understood to illustrate one manner ofproducing a self-heating sealant or adhesive for purposes ofunderstanding the disclosure and should not be considered as limitingthe embodiments.

The method 700 begins by providing sealant or adhesive (step 710). Instep 710, a sealant or adhesive may be chosen with consideration for theapplication of that sealant or adhesive to a particular substrate orsubstrates. In one embodiment, a sealant or adhesive may be chosen forapplication in sealing the periphery of a liquid crystal layer between aTFT array substrate and a color filter substrate and a heat-curableepoxy resin, such as previously disclosed herein, may be selected. Inother embodiments, a sealant or adhesive may be chosen for applicationin sealing or adhering other substrates. For example, a sealant oradhesive may be chosen for an application in adhering and formingelectrical connections between the transparent display/backlightelectrodes of an LCD module and a driver FPC and an anisotropicallyconductive adhesive, such as previously disclosed herein, may beselected.

Also in step 710, the curing temperature of the sealant or adhesive maybe determined. In addition, a desired thickness, or a desired range ofthickness, of a bond line of the sealant or adhesive suitable for theapplication may be determined in step 710. For example, the desiredthickness may be less than 5 microns or may be less than 2 microns. Adesired thickness may be determined in relationship to a particularcompliance, or range of compliance, values of the sealant or adhesive,and a temperature of the sealant or adhesive that may produce thecompliance may be determined.

The method 700 continues by providing multi-compartment microcapsules(step 720). Step 720 may, for example, correspond to the method 600(shown in FIG. 6) of producing a multi-compartment microcapsule having ashell-in-shell architecture with an inner shell contained within anouter shell, wherein the inner shell is adapted to rupture in responseto a compressive force and/or magnetic field according to someembodiments of the present disclosure.

At step 720, exothermic reactants compatible with the materials suitablefor forming a microcapsule may be chosen. The exothermic reactants maybe chosen to be inert with respect to the selected sealant or adhesive,the material of the microcapsule walls, or an isolating barrier within amicrocapsule when the reactants are not in contact. The exothermicreactants also may be chosen to be inert with respect to the sealant oradhesive or the outer microcapsule wall when the reactants are incontact, or such that the chemical products of the reaction are inertwith respect to the sealant or adhesive, outer microcapsule wall, andany remnants of the inner microcapsule wall or barrier.

Also at step 720, an amount of the first reactant and an amount of thesecond reactant may be determined. The amounts may be determined fromthe total amount of the reactants required to produce a desired amountof heat, the ratio of each reactant according to a reaction equation,the desired dimensions of the microcapsule, and the manner of isolatingthe reactants within the capsule. For example, a microcapsule may bedesired having a maximum dimension less than or equal to a desired finalthickness of a sealant or adhesive bond line, such as less than 0.5microns, and the amount of reactants may be chosen corresponding to thevolume available within a microcapsule formed according to thatdimension.

In addition, at step 720, one or more inner microcapsules, such asillustrated by microcapsule 302 of FIG. 3A, may be formed and the innermicrocapsules may contain a first or a second reactant. In variousembodiments, an inner microcapsule may be formed to contain a mixture offine iron powder and ferric nitrate, or may be formed to containhydrogen peroxide. The inner microcapsule(s) may be formed with acapsule wall configured to rupture with application of a compressiveforce. The force required to rupture an inner microcapsule wall may bedetermined from within the range of compressive force typical of thatapplied in the manufacture or repair of electronic assemblies (e.g.,during the process of assembling liquid crystal cells, during theprocess of assembling LCD modules, and the like).

Still further, at step 720, an outer microcapsule may be formedcontaining the inner microcapsule(s) and one or more other reactants, inthe manner of multi-compartment microcapsule 300 in FIG. 3A. Thereactant(s) contained in the outer microcapsule may be inert withrespect to each other and the microcapsule walls until in contact withone or more reactants contained in one or more inner microcapsules. Inone embodiment, an outer microcapsule may contain hydrogen peroxide, orother oxidizers, where one or more inner microcapsules contain finelypowered iron and ferric nitrate, or other reductants. In anotherembodiment, the outer microcapsule may contain finely powered iron andferric nitrate, or other reductants, where one or more innermicrocapsules may contain hydrogen peroxide or other oxidizers. Thecapsule wall of the outer microcapsule may be formed to not rupture atthe compressive force applied to rupture the capsule wall of the innermicrocapsule.

Alternatively, an embodiment may utilize a microcapsule having astructure as illustrated by multi-compartment microcapsule 310 in FIG.3B. In accordance with this alternative embodiment, at step 720, anouter microcapsule may be formed having one or more membranes 314, inthe manner of multi-compartment microcapsule 310 in FIG. 3B, forming two(or more) compartments within the outer microcapsule. The particularreactants described above may be contained within the compartments, andthe membrane(s) may be formed to rupture at compressive forces such asdescribed above with respect to the capsule wall of an innermicrocapsule.

In another alternative, an embodiment may utilize a microcapsule havinga structure as illustrated by multi-compartment microcapsule 320 in FIG.3C. In accordance with this alternative embodiment, at step 720, thecapsule wall of the inner microcapsule (i.e., the inner shell of themulti-compartment microcapsule 320) may be formed with one or moremagnetic nanoparticles so as to rupture under a particular magneticfield through magnetic stimulation of the one or more magneticnanoparticles and the outer wall of the microcapsule (i.e., the outershell of the multi-compartment microcapsule 320) may be formed so as tonot rupture under that magnetic field. For example, as described abovewith reference to FIG. 6, for the purpose of adapting the inner shell ofthe shell-in-shell microcapsule to rupture in responsive to a magneticfield, magnetic nanoparticles may be incorporated into the “inner shell”polyelectrolyte multilayer (i.e., the “Polymer” shown at stage 6(c)).The particular reactants described above may be contained within thecompartments.

The method 700 continues by determining an amount of themulti-compartment microcapsules (i.e., the multi-compartmentmicrocapsules provided in step 720) sufficient to increase thetemperature of an amount of the sealant or adhesive (i.e., the sealantor adhesive provided in step 710) to a curing temperature (step 730). Atstep 730, a proportional amount of microcapsules may be determined tomix within the sealant or adhesive. The determination may be madeaccording to the amount of heat required to raise a particular amount ofsealant or adhesive from the ambient temperature to the temperaturerequired to cure the sealant or adhesive (and/or produce the desiredcompliance of the sealant or adhesive), considering also the amount ofheat produced by compressing (or otherwise activating) a singlemicrocapsule.

The method 700 then concludes by dispersing the amount of themulti-compartment microcapsules with the amount of the sealant oradhesive (step 740). At step 740, an amount of sealant or adhesive toapply to substrate or substrates to be sealed or adhered may bedetermined, and a corresponding amount of multi-compartmentmicrocapsules may be mixed into the sealant or adhesive. For example, asealant or adhesive may cure at 100° C., i.e., a temperature of thesealant or adhesive approximately 75 degrees C. above room ambienttemperature. This example, utilizing the reactants and reactiondescribed in reference to FIG. 4A through FIG. 4D, may require at least0.6 grams of the combined amounts of the reactants dispersed within 30grams of the sealant or adhesive.

In this example, if we assume 30 g of sealant or adhesive is used for atypical application, and further assume a 2 wt % loading of themulti-compartment microcapsules, this yields 0.6 g of themulti-compartment microcapsules. Also, in this example, to achieve asuitable stoichiometry, 57% of the multi-compartment microcapsules willbe loaded with finely divided iron powder; 43% with an oxidizer yielding0.342 g Fe. This mass of iron particles will liberate 2.518 kJ. As afirst approximation, 30 g (0.03 kg) of sealant or adhesive requires 0.03kJ to raise its temperature 1° C. (1.00 kJ/kg C·0.03 kJ/C). Assuming inthis example that the heat capacity of the sealant or adhesive isequivalent to that of epoxy cast resin, the heat of reaction in thisexample would be sufficient to raise the temperature of the 30 g ofsealant or adhesive almost 84° C. (2.518 kJ/0.03 kJ/C=83.9° C.).Depending on the desired temperature boost, the loading level and/orstoichiometry can be adjusted.

FIG. 8 is a flow diagram illustrating an exemplary method 800 of curinga self-heating sealant or adhesive according to some embodiments of thepresent disclosure. In the method 800, the steps discussed below (steps810-830) are performed. These steps are set for the in their preferredorder. It must be understood, however, that the various steps may occursimultaneously or at other times relative to one another. Moreover,those skilled in the art will appreciate that one or more steps may beomitted.

The method 800 begins by providing a self-heating sealant or adhesive(step 810). Step 810 may, for example, correspond to the method 700(shown in FIG. 7) of producing a self-heating sealant or adhesiveaccording to some embodiments of the present disclosure.

In step 810, a self-heating TIM may be selected. The selection mayconsider particular properties of the sealant or adhesive and thesubstrate or substrates to be sealed or adhered. The particularproperties considered may include the thermal and/or electricalconductivity of the sealant or adhesive, the durability of the sealantor adhesive, the shear strength of the sealant or adhesive, the chemicalor physical suitability of the sealant or adhesive with the substrate orsubstrates to be sealed or adhered, the compliance of the sealant oradhesive at the ambient temperature, or the initial and desired finalthickness of the sealant or adhesive bond line between the substrates.Other considerations may apply to a particular assembly, devices,manufacturing process, or field repair process and will be evident toone of ordinary skill in the art.

The method 800 continues by applying the self-heating sealant oradhesive to the substrate or substrates to be sealed or adhered (step820). At step 820, a selected self-heating sealant or adhesive may beapplied in the initial bond line thickness.

Also at step 820, an amount of the sealant or adhesive may be determinedthat produces an initial bond line thickness between the substrates tobe sealed or adhered. The compliance of the sealant or adhesive at theambient temperature of manufacture or repair may determine the initialthickness of the sealant or adhesive. For example, in an embodiment, aninitial thickness of a sealant or adhesive may be 5.0 microns or more,and a final thickness of the bond line after heating the sealant oradhesive may be desired to be less than 2.0 microns

The method 800 then concludes by activating the self-heating sealant oradhesive by applying a stimulus (e.g., a compressive force, a magneticfield, ultrasound, or a combination thereof) to the self-heating sealantor adhesive (step 830). In some embodiments, at step 820, the substratesmay be joined together at the bond line of the sealant or adhesive andjoining the substrates may compress the sealant or adhesive. In otherembodiments, at step 820, the substrates may be pressed together tocompress the sealant or adhesive, until the sealant or adhesive maycure, at the bond line of the sealant or adhesive. Accordingly, thecompressive force applied to the sealant or adhesive may vary within arange typical of the manufacture of electronic or mechanical assemblies,or within a range of mechanical pressure applied to join the substratesuntil the sealant or adhesive has cured or otherwise had effect to sealor adhere the substrates.

Also at step 820, compressing the self-heating sealant or adhesive mayproduce an exothermic reaction acting to heat the sealant or adhesive,and the increased temperature of the sealant may produce a secondcompliance of the sealant or adhesive, and the second compliance of thesealant or adhesive may produce a desired final thickness of the sealantor adhesive bond line.

In addition, at step 820, the sealant or adhesive and the substrates maybe cooled to ambient temperature or to a temperature corresponding tonormal operation.

FIG. 9 is a flow diagram illustrating, through stages 9(a)-9(e), amethod 900 of assembling liquid crystal cells during thin-filmtransistor (TFT) liquid crystal display (LCD) panel fabrication, inwhich a self-heating sealant is used to seal the periphery of a liquidcrystal layer between a TFT array substrate and a color filter substrateaccording to some embodiments of the present disclosure. In the method900, the steps discussed below (steps 905-920) are performed. Thesesteps are set for the in their preferred order. It must be understood,however, that the various steps may occur simultaneously or at othertimes relative to one another. Moreover, those skilled in the art willappreciate that one or more steps may be omitted.

In each of the stages 9(a)-9(e), the structure is shown in across-sectional side view and a top view.

Stage 9(a). As is conventional, the method 900 of assembling liquidcrystal cells begins by printing a polyimide alignment film 920 on botha TFT array substrate 922 and a color filter substrate (928 shown instage 9(d)). These substrates are typically sized so that multiple(e.g., six, eight, nine, or twelve) cells can be producedsimultaneously. Only one cell is shown in FIG. 9 for the sake ofclarity. The surface of each polyimide alignment film is then rubbed(e.g., with a piece of cloth wound on a roller) to orient the polyimidemolecules in one direction.

Stage 9(b). After completing the rubbing process, a self-heating sealant924 is applied to the periphery of the TFT array substrate 920 (step905). The self-heating sealant 924 corresponds with the LCD panel mainsealant 102 shown in FIGS. 1 and 2. The self-heating sealant 924 may be,for example, a heat-curable epoxy resin in which the multi-compartmentmicrocapsules are dispersed. Alternatively, the self-heating sealant maybe, for example, a UV+heat-curable epoxy resin, such as LOCTITE ECCOBONDDS 6601, in which the multi-compartment microcapsules are dispersed. Inaddition, the TFT array substrate 920 may be coated with a conductingpaste (not shown) around its periphery to form electrical connectionsbetween electrodes on the color filter substrate and electrodes on theTFT array substrate. Alternatively, the self-heating sealant 924 may beapplied to the periphery of the color filter substrate.

Stage 9(c). The method 900 continues by spreading one or more spacers(step 910). Spacers control the cell gap and are sprayed onto the TFTarray substrate 922. Alternatively, the spacers may be sprayed onto thecolor filter substrate 928.

Stage 9(d). The TFT array substrate 922 and the color filter substrate928 are brought together, aligned, and subjected to pressure bonding toactivate the self-heating sealant 924 (step 915). For example, aconventional UV press (typically utilized to cure conventional UV-curingresins) or a conventional hot press (typically utilized to cureheat-curing resins) may be employed to exert a compressive force on theself-heating sealant 924 sufficient to rupture the isolating structuresof the multi-compartment microcapsules. If the self-heating sealant 924is a heat-curable epoxy resin in which the multi-compartmentmicrocapsules are dispersed, the multi-compartment microcapsules maygenerate the heat necessary for heat-curing. If the self-heating sealant924 is a UV+ heat-curable epoxy resin in which the multi-compartmentmicrocapsules are dispersed, the multi-compartment microcapsules maygenerate the heat necessary for post cure (i.e., subsequent toUV-curing). The substrate assembly may then be scribed (e.g., using adiamond wheel) and separated into individual cells (each cellcorresponds to a TFT LCD panel). Once separated, the empty cells arefilled with liquid crystal material by vacuum injection.

Stage 9(e). An end-seal sealant 930 is then used to seal the cell (step920). The end-seal sealant 930 may be a self-heating sealant. Theend-seal sealant 930 corresponds with the LCD panel end sealant 104shown in FIGS. 1 and 2. The end-seal sealant 930 may be, for example, aheat-curable epoxy resin in which the multi-compartment microcapsulesare dispersed. If the end-seal sealant 930 is a heat-curable epoxy resinin which the multi-compartment microcapsules are dispersed, themulti-compartment microcapsules may generate the heat necessary forheat-curing. Alternatively, the end-seal sealant 930 may be, forexample, a UV+ heat-curable epoxy resin, such as LOCTITE ECCOBOND DS6601, in which the multi-compartment microcapsules are dispersed. If theend-seal sealant 930 is a UV+ heat-curable epoxy resin in which themulti-compartment microcapsules are dispersed, the multi-compartmentmicrocapsules may generate the heat necessary for post cure (i.e.,subsequent to UV-curing). The multi-compartment microcapsules containedin the end-seal sealant 930 may be activated, for example, by acompressive force applied by a sealant dispenser (e.g., a dispensinghead used to dispense the end-seal sealant 930).

One skilled in the art will appreciate that many variations are possiblewithin the scope of the present invention. Thus, while the presentinvention has been particularly shown and described with reference toparticular embodiments thereof, it will be understood by those skilledin the art that these and other changes in form and detail may be madetherein without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A method of producing a self-heating sealant oradhesive, the method comprising: providing a sealant or adhesive;providing multi-compartment microcapsules each having a firstcompartment and a second compartment separated from each other by anisolating structure adapted to rupture in response to a stimulus,wherein the first and second compartments of each multi-compartmentmicrocapsule contain reactants that come in contact and react to produceheat when the isolating structure ruptures; adding the multi-compartmentmicrocapsules to the sealant or adhesive.
 2. The method as recited inclaim 1, wherein the stimulus is selected from a group consisting of acompressive force, a magnetic field, and combinations thereof.
 3. Themethod as recited in claim 1, wherein the sealant or adhesive isselected from a group consisting of an epoxy-based sealant, anacrylic-based sealant, a silicone-based sealant, and combinationsthereof.
 4. The method as recited in claim 1, wherein the sealant oradhesive is selected from a group consisting of an epoxy-based adhesive,an acrylic-based adhesive, a silicone-based adhesive, and combinationsthereof.
 5. The method as recited in claim 1, further comprisingdetermining an amount of the multi-compartment microcapsules sufficientto increase the temperature of an amount of the sealant or adhesive froma first temperature to a curing temperature, and wherein adding themulti-compartment microcapsules to the sealant or adhesive includesdispersing the amount of the multi-compartment microcapsules within theamount of the sealant or adhesive.
 6. The method as recited in claim 1,wherein the first compartment contains a metal and the secondcompartment contains an oxidizer.
 7. The method as recited in claim 1,wherein the multi-compartment microcapsules are shell-in-shellmicrocapsules each comprising an inner shell contained within an outershell, wherein the inner shell encapsulates the first compartment,wherein the outer shell encapsulates the second compartment, and whereinthe inner shell defines the isolating structure.
 8. The method asrecited in claim 7, wherein the first compartment contains iron, andwherein the second compartment contains hydrogen peroxide.
 9. The methodas recited in claim 7, wherein the first compartment contains iron andferric nitrate, and wherein the second compartment contains hydrogenperoxide.
 10. A self-heating sealant or adhesive, comprising: a sealantor adhesive; multi-compartment microcapsules distributed in the sealantor adhesive, wherein each multi-compartment microcapsule has a firstcompartment and a second compartment separated from each other by anisolating structure adapted to rupture in response to a stimulus,wherein the first and second compartments of each multi-compartmentmicrocapsule contain reactants that come in contact and react to produceheat when the isolating structure ruptures.
 11. The self-heating sealantor adhesive as recited in claim 10, wherein the stimulus is selectedfrom a group consisting of a compressive force, a magnetic field, andcombinations thereof.
 12. The self-heating sealant or adhesive asrecited in claim 10, wherein the sealant or adhesive is selected from agroup consisting of an epoxy-based sealant, an acrylic-based sealant, asilicone-based sealant, and combinations thereof.
 13. The self-heatingsealant or adhesive as recited in claim 10, wherein the sealant oradhesive is selected from a group consisting of an epoxy-based adhesive,an acrylic-based adhesive, a silicone-based adhesive, and combinationsthereof.
 14. The self-heating sealant or adhesive as recited in claim10, further comprising determining an amount of the multi-compartmentmicrocapsules sufficient to increase the temperature of an amount of thesealant or adhesive from a first temperature to a curing temperature,and wherein adding the multi-compartment microcapsules to the sealant oradhesive includes dispersing the amount of the multi-compartmentmicrocapsules within the amount of the sealant or adhesive.
 15. Theself-heating sealant or adhesive as recited in claim 10, wherein thefirst compartment contains a metal and the second compartment containsan oxidizer.
 16. The self-heating sealant or adhesive as recited inclaim 10, wherein the multi-compartment microcapsules are shell-in-shellmicrocapsules each comprising an inner shell contained within an outershell, wherein the inner shell encapsulates the first compartment,wherein the outer shell encapsulates the second compartment, and whereinthe inner shell defines the isolating structure.
 17. The self-heatingsealant or adhesive as recited in claim 16, wherein the firstcompartment contains iron, and wherein the second compartment containshydrogen peroxide.
 18. The self-heating sealant or adhesive as recitedin claim 16, wherein the first compartment contains iron and ferricnitrate, and wherein the second compartment contains hydrogen peroxide.19. A method of curing a self-heating sealant or adhesive, the methodcomprising: providing a self-heating sealant or adhesive, wherein theself-heating sealant or adhesive comprises a sealant or adhesive andmulti-compartment microcapsules distributed in the sealant or adhesive,wherein each multi-compartment microcapsule has a first compartment anda second compartment separated from each other by an isolating structureadapted to rupture in response to a stimulus, wherein the first andsecond compartments of each multi-compartment microcapsule containreactants that come in contact and react to produce heat when theisolating structure ruptures; activating the self-heating sealant oradhesive by applying the stimulus in an amount sufficient to rupture theisolating structure, thereby allowing the reactants to come in contactand react to produce heat.
 20. The method as recited in claim 19,wherein the stimulus is selected from a group consisting of acompressive force, a magnetic field, and combinations thereof.